1. Field of the Invention
The present invention relates to an improvement in a compact imaging module provided with an imaging sensor such as a CMOS (complementary metal-oxide semiconductor) sensor, CCD (charge-coupled device) sensor or the like, more specifically to an inexpensive compact imaging module that a high density mounting is possible by combining a case of resin formation and an existing circuit substrate.
2. Description of Related Art
Recently, there has been sold a phone such as a mobile phone, PHS or the like containing a digital camera function capable of taking a photograph, and users of the phone can send the photograph as an attached file of an e-mail. A great number of the mobile phones having the camera function each comprising a compact imaging module in which a solid-state imaging sensor such as a CMOS sensor, CCD sensor or the like and an optical member such as a lens, aperture stop or the like are installed and united in a case, similarly as a digital camera.
A conventional compact imaging module using the above-mentioned CMOS sensor is disclosed in Japanese Patent Laid-Open 2001-245217, hereinafter a basic structure thereof will be described.
FIGS. 6 and 7 illustrate a structure of the conventional compact imaging module 50 using the CMOS sensor 1. In FIGS. 6 and 7, 51 is a case which is formed by a resin and which is provided with a lens holding barrel portion 51a, a sensor containing portion 51b disposed on an lower surface of the lens holding barrel portion 51a, and a sensor window 51c between the lens holding barrel portion 51a and the sensor containing portion 51b. Disposed within the lens holding barrel portion 51a is an optical system member which includes an aperture stop member 4, lenses 2 and 3, and an IR cutting filter 5 disposed in turn from an imaging side of the optical system member.
52 is a circuit substrate, on which the CMOS sensor 1 as the imaging sensor is mounted by wire-bonding, a light receiving portion 1b of the CMOS sensor 1 is disposed to oppose to the sensor window 51c of the case 51. The compact imaging module 50 is structured by containing the circuit substrate 52 mounting the CMOS sensor 1 in the sensor containing portion 51b. 
However, the compact imaging module 50 having the structure as described above tends to be a large size and is not able to satisfy request for miniaturization.
Therefore, in order to satisfy further demand of miniaturization, a compact imaging module has been developed as disclosed in Japanese Patent Laid-Open 2001-333332, a basic structure thereof will be described referring to FIGS. 8 and 9, hereinafter.
In FIGS. 8 and 9, the same numerals are attached to the similar parts as in FIG. 7, and the overlapped description is omitted.
As shown in FIG. 9, a wiring pattern 62 is formed on an inner surface of a sensor containing portion 61b of a case 61. Mounting terminal portions 62a for mounting the CMOS sensor 1 and outside connecting terminal portions 62b drawn-out to a lower surface of the sensor containing portion 61b are integrally formed on the wiring pattern 62.
The CMOS sensor 1 is mounted on the case 61 by face down-bonding bumps 1a provided on the CMOS sensor 1 on the mounting terminal portions 62a. In FIG. 9, the CMOS sensor 1 is reversed and bonded on the case 61.
FIG. 8 shows a state of mounting the CMOS sensor 1 on the case 61, the lenses 2, 3, the aperture stop member 4 and the IR cutting filter 5 are contained in a lens holding barrel portion 61a of the case 61, similarly as in FIG. 7.
The CMOS sensor 1 is face down-bonded on the mounting terminal portions 62a of the wiring pattern 62 formed on the inner surface of the sensor containing portion 61b so that a compact imaging module 60 is structured.
In the state, the light receiving portion 1b of the CMOS sensor 1 is disposed to oppose to the sensor window 61c of the case 61, and configured to receive a signal light passing through the optical system member of the lens and so on. The signal light processed by the CMOS sensor 1 is outputted from the outside connecting terminal portions 62b through the wiring pattern 62 to the outside.
The structure shown in FIGS. 8 and 9 is referred to as a MID in which a three-dimensional conductive circuit is formed on a resin forming body constituting the case 61 without using the circuit substrate 52 shown in FIG. 7, the mounting of the CMOS sensor 1 and the formation of the outside connecting terminal portions are carried out simultaneously by the three-dimensional conductive circuit.
As a method for forming the three-dimensional conductive circuit on the resin forming body, there are a one-time forming method for forming a conductive pattern on a surface of the resin forming body by means of a transfer, and a two-time forming method for forming primarily a pattern forming portion by a plating grade resin, forming secondarily a pattern non-forming portion by a non-plating grade resin, and forming partially a plated pattern by use of a difference of the plating grades.
The compact imaging module structured by the aforementioned MID has a merit that further miniaturization can be achieved in comparison with the compact imaging module using the circuit substrate shown in FIG. 7, at the same time, there are problems as follows.
That is to say, it is difficult to form a fine pattern as in a pattern etching art used for pattern formation of a conventional circuit substrate, for the method for forming the three-dimensional conductive circuit on the resin forming body. Consequently, if a CMOS sensor having many pixels and high resolution is used as the imaging sensor, a pitch between narrow pads is requested, because a great number of terminals are required, the MID art cannot correspond to the circumstances.
Furthermore, in the compact imaging module of the MID structure, the cost of manufacture is higher because many manufacturing processes are required.